Radiant Floor Heat

One of our goals with the TREE House is to implement a variety of green technologies, materials, and strategies in order to be able to share information with visitors about how (and how well) they work.  With that in mind, we decided to mix things up with a few different strategies for heating and cooling. In conjunction with a tight and well-insulated house, we determined that a radiant floor heat system was the way to go in our basement (and future classroom).

With the basement being warmed from the bottom up, we figured that heat would transfer up, to the benefit of the first floor. We used the first winter as a test case to see how our mini-split heat pumps did on their own—without the radiant floor heat in the basement. See the Insulation and Air Sealing page to find out how things went. We plan to collect comparative data next year—with the radiant floor heat in place.

Through a network of wires or tubing set beneath the floor level, radiant floor heating systems circulate hot air, water, or electricity to warm the thermal mass of the floor (they can be installed in walls too).  This transforms floors into surfaces that provide even, steady heat, supplementing the warmth we try to generate in our homes when it’s cold outside.  Our system is water-fed, i.e., hydronic—the most efficient of the three styles.

A recent "Scientific American" article explains that efficiency gains from a radiant floor system “can be magnified significantly with good insulation and a well-designed system,” saving households hundreds of dollars a year. In a nutshell, “while tearing out old heating systems and/or replacing decent existing flooring might be overkill for the sake of moving to radiant heat, those embarking on new building projects or contemplating major renovations should certainly consider it.” Some states offer financial incentives to upgrade the energy efficiency of home heating systems.  To learn more about tax rebates or other incentives available here, check out the Database of State Incentives for Renewable Energy (DSIRE).

Radiant floor systems have a number of clear advantages, they are:

  1. efficient, putting the heat where you live, and not up above your head 
  2. quiet, virtually silent, with none of the engine-like sounds of furnaces blasting on or off
  3. cost-effective, saving you money on monthly heating bills
  4. hypoallergenic, with no dust mites, other particulates, or hot dry air being distributed through ductwork
  5. easy to install (as you can see from the pictures below)

Getting wire mesh panels down and connected. (Pictured here, students Zach Baker, Caitlin Joseph, and Devlin Geroski.)

Rolling out the tubing in looping patterns in our three “zones” and tying it to the wire mesh.  Each zone contains 300’ of tubing and its own return and supply connection to the manifold. (Pictured here, Associate Professor Debbie Kasper wrestling with what feels like a giant slinky, builder Jim Zella in the background, Zach Baker in foreground.)

Voila!  Now that the tubing is installed, we’ll add a layer of concrete and, over that (eventually), our floor finish.

The water in our system is heated by our hybrid heat pump/coil water heater. This appliance uses heat pump technology to absorb the heat in ambient air and then transfers it into the water. According to manufacturer specs, this water heater is 62% more efficient than a standard electric water heater of the same size.

This spring, we finally got the radiant floor system hooked up and running!  We have been enjoying a lovely 68F basement, while outside temps fluctuate wildly up and down. We’re excited to have a more useable space and we’re eager to see how our heated basement will affect next winter’s home performance.

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